An example of one type of intake system in an internal combustion engine comprises runners through which air is delivered from an air plenum to cylinder intake valves. Tuning of an engine intake system is beneficial in improving various aspects of engine operation, and for that purpose certain tuning mechanisms are present in certain engine intake systems.
One example of such an engine intake system comprises what are essentially a number of butterfly valves, each disposed within a respective runner, ganged together on a common shaft. The shaft is journaled for turning about its axis to correspondingly turn the butterfly valves in unison. Typically the shaft is turned by some type of actuator over a range that is no greater than 90° so that the butterfly valves are operable to impose a maximum restriction to airflow through the runners at one limit of the range and a minimum restriction at the opposite limit. When the butterfly valves are disposed in short runners, they are sometimes called short runner valves. When the short runner valves are closed, incoming air flows from the plenum to the cylinder intake valves through long runners. When the short runner valves are open, incoming air flows from the plenum to the cylinder intake valves through the short runners.
An intake system may also include a manifold tuning valve having a valve element that is journaled for turning about its own axis over a range that is also limited, for example a range of 90°.
Typically the plenum, runners, and associated valves are parts of what is sometimes called an intake manifold assembly, and it is common design practice to mount such an intake manifold assembly directly on an engine. Consequently, the intake manifold is subject to effects resulting from normal engine and motor vehicle operation, including vibration, air pulsation, and temperature extremes. These effects are felt in one way or another by the tuning mechanism.
One manifestation of these effects is tuning valve chatter. Chatter can occur when the short runner valves are closed and also when the manifold tuning valve is closed.
U.S. Pat. No. 6,637,397 addresses the matter of intake manifold tuning valve chatter by providing spring-loaded anti-chatter devices that apply forces against the valve shafts. Those anti-chatter devices comprise multiple parts that have to be individually installed, and a number of anti-chatter devices are required in just one engine intake system. Moreover, the anti-chatter devices are additional to valve actuators.